Many existing flight simulators employ faceted displays, with multiple panels of "out the window" visual information presented at different angles and with multiple vertices. Using a head-mounted display (HMD) in a faceted simulator can present visual artifacts not seen in the cockpit, including HMD imagery which appears slanted and with a distorted perspective compared to the imagery presented on the faceted simulator displays. Users viewing information presented across the vertices of the simulator display may notice anomalies due to the HMD imagery being "flat" while the vertex represents a "fold" in the displayed simulator imagery. Binocular HMDs present issues with vergence mismatch when integrated with faceted displays, where the vergence distance (the distance at which the user's eyes converge) to the HMD imagery stays constant while the vergence distance to the simulator imagery varies with head position. These effects could potentially lead to double-imaging (diplopia) and discomfort, and could also diminish the feeling of immersion.

In our previous research, adaptive vergence clearly led to improved comfort and utility compared to fixed vergence, and also led to increased performance on a targeting task. However, some users complained about the distorted perspective, and this may have also affected targeting performance. We have expanded upon those earlier results and examined the effects of mitigating these artifacts using a combination of image perspective warping, rotation and bending. We evaluated both adaptive vergence mitigation only, as well as adaptive vergence mitigation with image warping, rotation, and bending. For each experimental condition, we asked the users to report diplopia/comfort and we also measured their timed performance in a simulated targeting task. We conducted this experiment in a simplified two-facet display system with viewing distance ranging from 36 - 45 inches. Our results show that attempting to mitigate slant and vertex effects have no measureable increase in operator comfort and actually decrease operator performance. In addition, many subjects did not like the fact that the symbology bent into the vertex and moved in space to become coplanar with the out the window displays. Given our previous positive results from adaptive vergence alone, we would recommend not implementing slant and vertex mitigation, but instead just using adaptive vergence mitigation.